GEOCHEMICAL CHARACTERISTICS OF WATER AND SEDIMENT OF THE INDUS RIVER,TRANS-HIMALAYA, INDIA - CONSTRAINTS ON WEATHERING AND EROSION

The Indus river carries a huge amount of chemical and sediment load wh ile traversing the Himalayas. The present study deals with the chemist ry of major ions (Ca, Mg, HCO3, Na, K, Cl, SO4, SiO2) and trace metal contents (Ba, Sr, Zn, Ni, Cu, Co, Mn) of the river Indus, one of its m ajor tributaries, the river Beas, many adjoining hot and cold water sp rings and the high altitude lake (similar to 5700 m) Kyung Tso. Althou gh anthropogenic activities like farming, grazing and tourism have sta rted in large parts of this terrain, our study indicates that chemistr y of Indus water is influenced mostly by the lithology of the basin an d most of its ionic concentration appears to have been derived from we athering of carbonates and silicates in the catchment area. For the fi rst time, bed and suspended sediments of the river Indus have also bee n studied and compared with average Post Archean shale (PAS) and greyw acke. The sediments of the Indus river in its headwater region closely reflect the exposed portion of the crust in its catchment area. The h eadwater part of the Indus Basin in Ladakh and Karakorum is characteri sed by rapid uplift and, therefore, subject more to intense physical w eathering than chemical weathering, as is evidenced by the suspended a nd dissolved load carried by the river. Physical weathering and erosio n is expected to have major controls on the grain size and therefore t he chemical nature of the sediments. (C) 1998 Elsevier Science Ltd. Al l rights reserved.